Tilt/Trim issues

[79Merc175]

Hello - I've got a '79 V175 that was having an issue with tilt/trim where I'd have to tap the top of the AC motor to get it to run. This sounded like a classic case of it needing new motor brushes so I bought a repair kit (commutator and brushes) and rebuilt it after thoroughly cleaning the old brush dust from the motor. After the rebuild it now doesn't run at all. To add to this in the midst of troubleshooting I now also don't hear any audible click from the solenoids used for up/down operations. I've replaced the solenoids this weekend and took the AC motor back apart to double-check everything but still my tilt/trim is dead. I've checked for blown fuses, burnt wires and the like but everything appears to be sound from that perspective. I'm sure I now have multiple issue but am looking for suggestions on how to narrow this down and other things to look for.

Thanks In Advance!!

 

[hkeiner]

Re: Tilt/Trim issues

A Mercury OEM shop manual is the best source for information in troubleshooting the trim system. If you don't have one and don't plan on getting one, below are a few pages from my manual which may help. All you need is a multi-meter, an understanding of the wiring diagram, and a systematic approach to locating the failed component/connection/wire/etc.

 

[79Merc175]

Re: Tilt/Trim issues

Thanks for the reply and for the pictures however mine has the old prestolite T&T pump which has a round AC motor and rectangular resevoir. There are only two wires that come from the AC motor, one blue and one green and there are two solenoids on my set up. I have a seloc for this but didn't see a wiring diagram that looked very similar.

Does anyone else have any wiring diagrams for the prestolite T&T pump and/or advice, suggestions, etc.

MANY THANKS!

 

[hkeiner]

Re: Tilt/Trim issues

Maybe this one is closer to what you have. It is for ser # 5124981 to 5363918. If you provide the serial number for your motor, there is a better chance of matching it to the correct wiring diagram. The cover pages on the Mercury shop manuals typically only indicate the applicable serial number ranges and not model years.

http://www.maxrules.com/oldmercs/Wiring/1966ona/52.jpg


http://www.maxrules.com/MERCwireindex.html

 

[79Merc175]

Re: Tilt/Trim issues

hkeiner you nailed it with the S/N range and I can't say thank you enough for this invaluable information. it's members like you who inspire those of us who are a little green at this!

 

[Chris1956]

Re: Tilt/Trim issues

You may bypass the solenoids and therefore isolate them as bad/good.

Remember that two wire motor uses ground to complete the circuit. +12V goes onto the blue wire, and -12VDC on the black wire or trim bracket to trim up. +12V goes on the green wire, -12V on the black wire or PTT bracket to trim down.

In addition there is a bimetal overload circuit breaker inside the PTT motor. If it gets some dirt on the contacts, it will open, killing the circuit.

 

[79Merc175]

Re: Tilt/Trim issues

Hi Chris1956- thanks for the reply. I'm a little confused as to the wires I see off of the motor. From the motors field housing there are only two, one looks to be a greenish color and the other a blue but this could also be black i guess as the age may have changed the color a bit. The only other wire on the motor is one that appears to be a ground and its connected using a terminal ring to one of the 2 long screws that go thru the cap and mount the motor to the resevoir. I'll try to test by-passing the solenoids as you said but as far as the bimetal overload circuit breaker goes is there a way to know whether or not this is tripped other than if the motor fails to run while going straight to a power source w/out the solenoids?

 

[Chris1956]

Re: Tilt/Trim issues

If the motor shows an open circuit when testing on the green and black wires, and the blue and black wires.

The point is the motor is really a three wire motor. Black, blue and green. Power is applied to either the blue or green wires, and ground is on black that completes the circuit.

 

[79Merc175]

Re: Tilt/Trim issues

Thanks again Chris1956; I think I may finally have my brain wrapped around this and will do some t-shooting.

One other thing that I keep seeing different answers for though is around the solenoids and if you *should* or *should not* hear a click when they're functioning properly. Any insight into this that you can share?

 

[hkeiner]

Re: Tilt/Trim issues

One other thing that I keep seeing different answers for though is around the solenoids and if you *should* or *should not* hear a click when they're functioning properly. Any insight into this that you can share?

Listening for a non-click is one way to check if a solenoid is dead/stuck. A non-click, however, could be due to other reasons and hearing a click does not guarantee that the solenoid is working OK. A more reliable way to troubleshoot is to use a multimeter and check if there is voltage where there should be voltage and ground where there should be ground. A good way to confirm that the solenoid is working properly is to use a multi-meter to check for voltage on the circuit(s) feeding juice from the solenoid to the trim motor when the trim button is activated. If it is, then the motor or a bad ground is suspect.

 

[Chris1956]

Re: Tilt/Trim issues

Solenoids may still click and not function. The best test at that point is to bypass them, and if the trim works, and the solenoids have power and ground to the primary winding (small wires), it is bad.